[App_rpt-users] CM119 USB interface

[Kevin Custer]

Howdy Mark,

This particular group is for supporting the "official" AllStarLink 
distribution of Asterisk and app_rpt called ASL1.01, and legacy 
distributions like ACID and DIAL.  As such, we don't generally get into 
the discussions and support for HamVoIP.  Those folks have their own 
support system.  However, I'll attempt to answer your questions.  
HamVoIP doesn't recommend the use of usbradio, however it's fully 
supported in ASL 1.01.  My suggestion is you download ASL 1.01 and give 
it a try.
<https://wiki.allstarlink.org/wiki/Main_Page>

USBradio is one of the features that I really like about AllStarLink.  
When fed with discriminator audio, the software will determine the noise 
squelch and CTCSS detection, eliminating the need for hardware 
modifications and obtaining the right logic signals for COS and CTCSS 
(sometimes not as easy as one would like).  Then, feeding the FM 
modulator directly with audio that's been filtered, pre-emphasized and 
limited, makes all transmitters sound the same no matter who made them.  
The noise squelch detection is as close to a Motorola M6709 as you can 
get.  That's often thought of as the high water mark in noise squelch 
circuitry.  The CTCSS detection is as good as any COM-SPEC product of 
past or present, also thought of as the best in the industry.

Since we're on the subject of usbradio, there's something else that I 
should mention.

Since 2008, a C-Media integrated circuit of some kind has been used as 
the heart of most radio to computer audio interfacing in AllStar Link.  
The CM108, CM119 and CM119A are used in most of the adapters to date.  
Some manufacturers have settled on the new CM119B chipset.  In my 
opinion, the adapters based on this chipset shouldn't be used with 
usbradio. Why? All of these components are similar, except the CM119B.  
The "B"component includes a few changes which are significantly 
different. These differences may not allow the CM119B to operate 
correctly with AllStar.  The two big differences are the lack of crystal 
stability, and a new "feature' called Pop Filtering on the MIC input.  
In review of the spec sheet for the CM119B in comparison with its prior 
counterparts, the pop filter rolls off the low end frequency response.  
This slope might be enough to cause unreliable detection of CTCSS when 
using the usbradio channel driver, especially on lower tone 
frequencies.  I'm also concerned that without the crystal time base, the 
RC stability of the CM119B will result in unreliable CTCSS detection 
caused by frequency drift. This is especially true in systems where the 
audio adapter is subjected to wide ambient temperature changes, as found 
in shelters that are not environmentally controlled.  In addition, there 
are audio scaling differences between the prior chipsets, and the 
CM119B.  The scaling differences are currently being worked out in software.

In conclusion, the CM119B may be fine when used with the simpleusb 
channel driver, but there are lots of people that rely on the DSP of 
app_rpt for software noise squelch and CTCSS detection. I recently 
purchased several hundred CM119A components directly from C-Media.  
That's what I will continue to supply in my radio adapter offerings, as 
we know it works in every distribution, no matter if it's simpleusb or 
usbradio.

Kevin W3KKC

On 1/1/2019 9:19 AM, Mark DuMoulin wrote:
> Kevin,Brian;
>
> I have been trying to set up use of radiousb instead of simpleusb. I see here Brian is doing that with the issues he is having.
> I can't get nearly that far.
> I am running hamvoip rc19 on some and recently downloaded stretch.
> In both cases I set the usbradio module to load however I cannot get the driver to work and keep getting asterisk failures.
> Additionally the menus set up by the programmer show only simpleusb-radio-tune not radio-tune-menu.
> Is there another image or procedure I need to run to get this started?
>
> Tnx,
> Mark
> WB2ERS